1. Field of the Invention
The present invention relates to a light source apparatus capable of correcting changes in hue, to a display apparatus provided with this light source apparatus and capable of correcting the hue of a display, to a terminal apparatus equipped with this display apparatus, and to a method for controlling these apparatuses.
2. Description of the Related Art
Because of their thin profile, light weight, small size, low energy consumption, and other advantages, display apparatuses that use liquid crystals have been widely deployed and used in a range of devices that includes monitors, televisions (TV: Television), and other large terminal apparatuses; notebook-type personal computers, cash dispensers, vending machines, and other mid-sized terminal apparatuses; and personal TVs, PDAs (Personal Digital Assistance: personal information terminal), mobile telephones, mobile gaming devices, and other small terminal apparatuses. Since the liquid crystal molecules themselves are non-self-emitting molecules that do not emit light on their own, some kind of light source is needed in order for the display to be perceived. Liquid crystal display apparatuses can be generally classified as transmissive, reflective, or transflective (using transmitted light and reflected light jointly) according to the type of light source used. Energy consumption can be reduced in the reflective type, since it can utilize external light in the display apparatus and there is no need to provide the display apparatus with a light source, but contrast and other aspects of display performance are inferior compared to the transmissive type. Therefore, transmissive and transflective liquid crystal display apparatuses are currently in the mainstream. In transmissive and transflective liquid crystal display apparatuses, a light source apparatus is installed on the back surface of a liquid crystal panel, and a display is created using the light emitted by the light source apparatus. Specifically, a light source apparatus that is separate from the liquid crystal panel is essential in current mainstream liquid crystal display apparatuses.
The display performance of terminal apparatuses has been improved with recent technological advances, and while these apparatuses have previously only been capable of monochromatic characters, they have recently become capable of displaying color image information of higher definition. In a liquid crystal panel capable of displaying color, each of the pixels is configured from red, green, and blue sub-pixels, and the sub-pixels of these three colors have color filters corresponding to the respective colors. Multicolor displays are formed by controlling the combination of the transmittances of these sub-pixels. Specifically, current mainstream liquid crystal panels have color filters as constituent elements, and the color reproduction areas on a chromaticity diagram are substantially established according to the spectroscopic characteristics of the color filters and to the spectrum of light emitted from the aforementioned light source apparatus. In general, the spectroscopic characteristics of the color filters and the matching of the light source spectra are vital to enlarging the color reproduction areas and displaying bright primary colors. Specifically, the spectroscopic characteristics of each color in the color filters are designed so that the respective transparent wavelengths do not overlap, and the light source spectra are set so that the emitted light has peaks in each of the red, green, and blue wavelength ranges.
Light-emitting diode (LED) technology in particular has recently been rapidly developing, and LEDs have therefore been used as light sources in the display apparatuses of not only portable terminal apparatuses, but also of larger terminal apparatuses. Particularly, LEDs corresponding to the three light colors red, green, and blue are used as light sources, whereby sharper emitted light peaks for the three primary colors can be preserved in the light source spectrum, making it possible to enlarge the color reproduction areas and to achieve a brighter display. However, a technique for achieving balance among the colors is vital in cases in which red-green-blue LEDs or other multicolor LEDs are used as light sources. In cases in which this balance is disrupted for any reason, the hues of the light sources change, and the hue of the display therefore also changes. In view of this, a technique for achieving this color balance, i.e., a method for detecting and controlling the state of the colored light-emitting elements has been proposed.
FIG. 1 is a schematic structural view showing the first conventional liquid crystal display apparatus equipped with a light source control device and described in JP-A 2004-361618. As shown in FIG. 1, the first conventional liquid crystal display apparatus 1001 equipped with a light source control device is composed of a liquid crystal panel 1002, a liquid crystal driver 1006 for driving the liquid crystal panel 1002, a display control circuit 1007 for supplying a signal to the liquid crystal driver 1006, a backlight 1003 disposed on the reverse side of the liquid crystal panel 1002 as seen from the viewing side, a backlight control circuit 1005 for controlling the backlight, and a light detector 1004 disposed on the viewing side of the liquid crystal panel 1002.
The liquid crystal panel 1002 has a liquid crystal display unit 1002a, which is a display area for displaying information; and a large number of pixels are disposed in the liquid crystal display unit 1002a. These pixels are arranged so that each set of three pixels includes a red, green, and blue pixel in order to achieve a color display. The pixels of these three colors are obtained by forming color filters of each color on a substrate, which is a constituent element of the liquid crystal panel 1002.
Furthermore, a detection pixel 1002b that does not function as a display is formed on part of the periphery of the liquid crystal display unit 1002a of the liquid crystal panel 1002. This detection pixel 1002b is composed of three detection pixels, for the colors red, green, and blue. The detection pixels for the three colors are obtained by forming color filters of each color on a substrate, in the same manner as the display pixels of the liquid crystal panel 1002. Specifically, the pixels in the liquid crystal display unit 1002a and the detection pixel 1002b are formed under the same conditions as when the liquid crystal panel 1002 is manufactured, and therefore have the same characteristics. Accordingly, the state of the detection pixel 1002b is a reflection of the state of the pixels of the liquid crystal display unit 1002a. 
The backlight 1003 functions as a light source for the liquid crystal panel 1002, and the backlight has as constituent elements a red light-emitting diode, a green light-emitting diode, and a blue light-emitting diode. The liquid crystal panel 1002 is illuminated with white light that is a mixture of these three colors. Furthermore, these three light-emitting diodes are connected to the backlight control circuit 1005, and are configured so that the emission intensities of the three colors are controlled individually. Specifically, the backlight 1003 is configured so that light from the red, green, and blue light-emitting diodes is mixed and white light is emitted, and since color changes are corrected in the liquid crystal panel 1002, which uses the white light as a light source, the backlight control circuit 1005 can adjust the emitting intensities of the light-emitting diodes of each color.
The light detector 1004 is configured from three light detectors that correspond to the red, green, and blue detection pixels 1002b. The output from these light detectors 1004 is inputted to the backlight control circuit 1005.
In the first conventional liquid crystal display apparatus equipped with a light source control device and described in JP-A 2004-361618 and that is configured in this manner, the light detector 1004 detects the intensities of each color via the red, green, and blue detection pixels 1002b. The pixels are formed on the liquid crystal panel 1002 and have the same conditions as the pixels of the liquid crystal display unit 1002a. The result is inputted to the backlight control circuit 1005. The backlight control circuit 1005 operates so as to differentiate the inputted results, and in cases in which it is determined that the color balance is disrupted and the desired chromaticity has been lost, the backlight control circuit adjusts the light intensity of the light-emitting diode of the corresponding color of the backlight 1003 and maintains a specific chromaticity. In one example, the emission intensity of the red light-emitting diode of the backlight 1003 is adjusted to maintain the desired chromaticity in cases in which a deviation from the desired value is detected in the intensity of red light. This detection is based on a signal from the red light detector 1004 disposed facing the detection pixel 1002b for red light. The same applies to green and blue light. The states of the light-emitting diodes for each color are thereby controlled so that the hue of the display does not change even in cases in which a plurality of light-emitting diodes that emit light in different colors is used. Since the color filter characteristics and liquid crystal characteristics of the liquid crystal panel 1002 are also taken into account to control the states of the light-emitting diodes of each color, these effects can be prevented and chromaticity can always be stably maintained even in cases in which the color filters change over time.
FIG. 2 is a schematic structural diagram showing a second conventional display apparatus equipped with a light source control device and described in SID 05 Digest p. 1376-1379. As shown in FIG. 2, the second conventional display apparatus 2001 equipped with a light source control device is composed of a liquid crystal display panel 2002; a backlight 2003 disposed on the reverse side of the liquid crystal display panel 2002 as seen from the viewing side; a light-emitting diode drive circuit module 2005 for driving the light-emitting diodes that are the constituent elements of the backlight; a light-emitting diode control module 2006 for controlling the light-emitting diode drive circuit module 2005; a light sensor module 2007 for outputting the states of the light-emitting diodes to the light-emitting diode control module 2006; and red, green, and blue light sensors 2004 connected to the light sensor module 2007 and assembled on the liquid crystal display panel 2002.
The backlight 2003 functions as a light source for the liquid crystal display panel 2002. This backlight has a red light-emitting diode, a green light-emitting diode, and a blue light-emitting diode as constituent elements, and the liquid crystal display panel 2002 is illuminated with white light that is a mixture of these three colors.
The light sensor 2004 is a photodiode formed from a non-crystalline silicon layer used as a semiconductor layer of a thin-film transistor that constitutes the pixels of the liquid crystal display panel 2002. The light sensor is formed on parts (e.g., upper and lower regions) of the liquid crystal display panel 2002 that lie outside the display area. Since the light sensor 2004 detects the three color red, green, and blue individually, color filters equivalent to the color filters of the pixels are set into the irradiated side of the light sensor 2004.
In the second conventional display apparatus equipped with a light source control device and described in SID 05 Digest p. 1376-1379 and that is configured in this manner, the light sensor 2004 detects the intensities of red, green, and blue light; the results are inputted to the light sensor module 2007 to determine the balance of the colors; the light-emitting diode control module 2006 controls the light-emitting diode drive circuit module 2005 on the basis of these results; and the light-emitting diodes for each color constituting the backlight 2003 are driven. It is thereby possible to inhibit occurrences in which the balance of the colors is disrupted and the desired chromaticity is lost, and changes in hue caused by changes in temperature and temporal changes can be reduced in particular. Therefore, the hue can always be stably maintained. In the present conventional example, since the light sensor is formed as an integral part of the liquid crystal display panel, there is no need to provide a separate light sensor outside of the liquid crystal display panel, the device can be reduced in size, and costs can be lowered.
However, the above-described conventional display apparatuses equipped with a light source control device are subject to the following problems. Specifically, in the first conventional display apparatus equipped with a light source control device, a minimum of three light detectors or light sensors are needed for the colors red, green, and blue, and it is therefore difficult to reduce the size of the detectors and controllers, and it is also difficult to lower costs.
In the second conventional display apparatus equipped with a light source control device, the light sensor is formed integrally with the liquid crystal display panel. It is therefore easier to reduce size and lower costs than with the first conventional display apparatus, which is equipped with a light source control device and in which the light detector was provided separately from the liquid crystal display panel. However, three light sensors are needed for the colors red, green, and blue in the second light source control device. A greater number of connections with the light sensor module is therefore provided to the exterior of the liquid crystal display panel. Not only is it difficult to reduce size owing to these connections, but reliability is also reduced, and it is difficult to lower costs. Furthermore, since three light sensors correspond to the colors red, green, and blue, separate wavelength filters are needed and it is difficult to lower costs any further.